Winslow T. Oddfellow is the deuteragonist and occasionally an antagonist of CatDog. He is a mouse who found CatDog as a baby and took care of them ever since. Winslow lives in CatDog's House in the hole in the wall and speaks with a Brooklyn accent. Winslow is always full of sarcastic remarks about anything and everything. He's very sneaky and underhanded with CatDog, especially with Cat. Winslow and Cat do not get along at all, because he's always getting Cat in trouble (as well as the fact that cats chase and eat mice). However, it was eventually revealed that Winslow may be afraid of Cat, because of Cat trying to eat him once. Dog, however, does not mind Winslow and is friendly with him. Deep down, he has a very big heart and loves CatDog and at some point act as CatDog's conscience and guidance of living in society, but acts out against them because he is jealous of how close they are. When he laughs, he goes "Heh Heh". His catchphrase is "What are you, nuts?" (pronounced "Whatta you, nuts?"). He is voiced by Carlos Alazraqui affecting a New York accent, who also voices Lube and a few one-time characters.